Petrogenesis, zircon U–Pb age, and geochemistry of the A-type Mogou syenite, western Henan Province: Implications for Mesozoic tectono-magmatic evolution of the Qinling Orogen

Abstract

The Mogou syenite intruded into the Mesoproterozoic Xiong'er Group is the main lithostratigraphic unit, along the southern margin of the North China Craton (NCC). This paper reports zircon LA-ICP-MS data, whole-rock major and trace element compositions of late Triassic magmatic rocks in the Mogou syenite, in order to constrain the formation age of the Mogou syenite, research the origin and evolution of the magma and analyse the geodynamic setting of the Qinling Orogen (QO) in Late Triassic. These rocks consist of medium-to coarse-grained syenite and fine-grained quartz syenite. Zircon U-Pb dating yields a crystallization age of 226.5±2.7 Ma. The syenites are characterized by high SiO 2 (63.49-72.17%), alkali (K 2 O+Na 2 O of 11.18-15.38%) and potassium (K 2 O/Na 2 O of 2.88-28.11), are peralkaline or metaluminous (molar A/CNK of 0.87-1.02) and belong to shoshonite series. The syenites have ΣREE of 33.01-191.30 ppm, LREE/HREE of 14-20, (La/Yb) N of 11-24, with LREE-rich distribution pattern and obvious differentiation between HREE and LREE. Eu anomalies are positive for the medium-to coarse-grained syenite and weakly negative for the fine-grained quartz syenite. In addition, the syenites are enriched in large-ion lithophile elements (Ba, K, Sr, and Pb) but depleted in high strength field elements (Ti, Ta, Nb, Zr, and Hf), and have high differentiation indices of 91.69-97.06. These geochemical features indicate that the primary magma of the Mogou syenite most likely originated from a mantle source with minor crustal component, and underwent a fractional crystallization process during its emplacement. The late Triassic A-type Moguo syenite along the southern margin of the NCC was generated in the late stage of the syn-collision event of QO, recording a transition period from compression to extension at around 227 Ma.

Geochronology and fluid source constraints of the Songligou gold‐telluride deposit, western Henan Province, China: Analysis of genetic implications

“…The Proterozoic-Paleozoic subduction of the Shangdan oceanic crust Dong et al, 2011;Yang et al, 2003) and Mesozoic subduction of the Izanagi plate Liu, Gurnis, Ma, & Zhang, 2017) beneath the NCC could both contribute to the metasomatism of the NCC (Xu, Zheng, & Zhao, 2011b;Yang, Teng, Zhang, & Li, 2012;Li, 2015;Song et al, 2016). The presence of a metasomatized lithospheric mantle beneath the southern margin of the NCC has also been supported by the emplacement of many intrusions, including the 245-210 Ma Mogou alkali pluton Lu, Liang, Bai, & Lu, 2013;He et al, 2016), the 225-209 Ma Huangshuian and Huanglongpu carbonatites (Stein et al, 1997;Huang, Wu, Du, & He, 1994;Huang, Hou, Yang, Li, & Xu, 2009;Du et al, 2004;Xu et al, 2011a;Cao et al, 2014;Song et al, 2015Song et al, , 2016, the ca.160 Ma Xinyang peridotitic xenolithos (Zheng, Sun, Zhou, & Robinson, 2005, Zheng et al, 2008; enriched by South China), the 129 Ma Huanglongpu diabase dikes (Zhao, Mao, Ye, Xie, & Yang, 2010), and the 122 Ma Tianqiaogou monzodiorites (Gao, Zhao, Bao, & Yang, 2014).…”

Triassic alkaline magmatism and mineralization in the Xiong'ershan area, East Qinling, China

“…LA–ICP–MS U–Pb analyses on zircon grains indicate that the Mogou pluton was emplaced between 245.5 ± 8.0 and 210.4 ± 2.0 Ma (J. Cao, Ye, Li, Zhang, et al, ; X. He et al, ; R. Lu, Liang, Bai, & Lu, ). X.…”

“…X. He et al () proposed that the Mogou syenite records a transition period from compression to extension at ~227 Ma. J. Cao, Ye, Li, Zhang, et al () suggested that the early phase of the Mogou pluton was formed in a local extensional setting during the collision process, and the late phase was emplaced in a post‐collision setting.…”

“…Available geochronological data suggest that the Mesozoic magmatic event and mineralization mainly occurred in two periods: (a) Triassic (255–208 Ma) syenite magmatism represented by the Mogou pluton and several Au, Mo, and Cu deposits (e.g., M. Cao et al, ; X. H. Deng, Chen, Santosh, Yao, & Sun, ; Gao, Mao, Ye, & Li, ; Gao, Ye, Mao, & Li, ; X. He et al, ) and (b) Middle Jurassic to Early Cretaceous (160–110 Ma) granitic magmatism and numerous Au, Mo, and Pb‐Zn‐Ag deposits (e.g., Bao, Sun, Zartman, Yao, & Gao, ; Mao et al, ; K. F. Tang, ; Tian et al, ).…”

“…Previous studies mainly focused on the Middle Jurassic to Early Cretaceous magmatic–hydrothermal events associated with the granitoid intrusions and related polymetallic mineralization (J. Deng, Gong, et al, ; Y. G. Han, Zhang, Pirajno, & Zhang, ; Mao et al, , ), mainly focusing on individual Triassic deposits (M. Cao et al, ) or the petrogenesis of the intrusions such as the Mogou pluton (J. Cao, Ye, Li, Zhang, et al ; X. He et al, ). However, comprehensive analysis on the probable genetic linkage between the Triassic magmatism and polymetallic mineralization is important to characterize the regional metallogeny in view of the exploration potential.…”